Autophagy and apoptotic machinery caused by Polygonum cuspidatum extract in cisplatin­resistant human oral cancer CAR cells.

Polygonum cuspidatum (Hu Zhang) is a traditional Chinese medicine (TCM) and has been revealed to exert anticancer, anti­angiogenesis, anti­human immunodeficiency virus (HIV), anti­hepatitis B virus, anti­microbial, anti­inflammatory, and neuro­protective bio­activities. However, the effect of P. cuspidatum extract (PCE) on drug­resistant human oral cancer cells regarding cell death is not fully understood yet. The present study was undertaken to explore the induction of autophagic and apoptotic cell death and to investigate their underlying molecular mechanisms in PCE­treated cisplatin­resistant human oral cancer CAR cells. Our results revealed that PCE was determined via HPLC analytic method, and it was revealed that resveratrol may be a major compound in PCE. The data also demonstrated that PCE reduced CAR cell viability in a concentration­ and time­dependent response via an MTT assay. PCE had an extremely low toxicity in human normal gingival fibroblasts (HGF). Autophagic and apoptotic cell death was found after PCE treatment by morphological determination. PCE was revealed to induce autophagy as determined using acridine orange (AO), LC3­GFP, monodansylcadaverine (MDC) and LysoTracker Red staining in CAR cells. In addition, PCE was revealed to induce apoptosis in CAR cells via 4',6­diamidino­2­phenylindole (DAPI)/terminal deoxynucleotidyl transferase dUTP nick­end labeling (TUNEL) double staining. PCE significantly stimulated caspase­9 and ­3 activities as revealed using caspase activity assays. PCE markedly increased the protein levels of Atg5, Atg7, Atg12, Beclin­1, LC3, Bax and cleaved caspase­3, while it decreased the protein expression of Bcl­2 in CAR cells as determined by western blotting. In conclusion, our findings are the first to suggest that PCE may be potentially efficacious for the treatment of cisplatin­resistant human oral cancer.